HISTOEICAL. 21 



New Species of Crinoidea, Albany, 1861," in which he gave on eighteen 

 pages preliminary notices of one hundred and eleven species, A large num- 

 ber of these descriptions remain in that shape to this day, while some of the 

 species were redescribed by him in the Boston Journal of Natural History, 

 Vol. Yll. In the Paleontology of New York, Vol. III., Hall described 

 twenty-six species from the Helderberg groups, — some of them, however, 

 from arm or stem fragments, — and from eighty to ninety additional ones 

 through the ditf erent Annual Reports of the New York State Museum. 



A large number of species were described by Meek and Worthen, 

 and after Meek's death by Worthen ; they amount to two hundred and 

 seventy species, with ten new genera, all well illustrated. Another lot was 

 described by Lyon and Casseday, and by Lyon individually ; in all thirty-one 

 species, with six new genera. Dr. C. A. White described thirty-five species, 

 and made three new genera. In Canada, E. Billings described some forty 

 species from the Trenton and Hudson River groups, with seven new genera. 

 In later years the most prolific species-maker was S. A. Miller, who increased 

 the number of species quite considerably. Many of his species have proved 

 to be synonyms, and while some of his new genera will be accepted by 

 every writer, others will go into obhvion. Additional species were described 

 by Whitfield, Wetherby, Ulrich, Barris, S. H. Williams, Whiteaves, Ringue- 

 berg, Wachsmuth and Springer, Walter R. Billings, Keyes, Rowley and 

 Hare, and others. 



The American Palaeontologists followed the terminology of De Koninck, 

 and their descriptions, as a rule, are concise and readily understood. But 

 few writers besides ourselves discussed morphological questions, and S. A. 

 Miller, Prof Chapman, and we, are the only ones who attempted to classify 

 the Crinoids. 



Billings, like most of the earlier writers, believed that the opening in the 

 disk of Palaeozoic Crinoids represented mouth and anus combined.^ He 

 pointed out that the grooves and galleries, passing out from the centre of 

 the disk at the inner floor, are connected with the ambulacral system, and 

 communicate through the arm openings with the arm grooves, but do not 

 enter the tegminal aperture, which he found to be interambulacral. When 

 Billings took up this question again in 1869,t presuming that the aperture 

 represented the mouth, he concluded that in the earlier Crinoids, in Blas- 



* Geol. Surv. of Canada; Decade IV. pp. 14 to 17- 



f Notes on the Structure of the Crinoidea, Cystidea and Blastoidea (Amer. Journ. of Sci. and Arts (2d 

 series), July, 1869, and January and September, 1870. 



